#include<stdio.h>
void main()
{
     float mu = 1.0;
	 float sum = 0;
	 float pi = 0;
	 int flag = 1;
	 
	 while(1/mu > 0.0001)
	 {
	       sum = sum + flag/mu;
		   mu = mu+2;
		   flag = -flag;
	 }
	 pi = 4*sum;
	 printf("%f ",pi);
}